Elliptical conoidal sound reproducing diaphragm



Dec. 15, 1953 HURLEY 2,662,606

ELLIPTICAL. CONOIDAL SOUND REPRODUCING DIAPHRAGM Filed Jan. 31, 1950 RuBERT E. EURLEY Gttorneg Patented Dec. 15, I953 ELLIPTICAL CONOIDAL SOUNDREPRODUCING DIAPHRAGM Robert E. Hurley, Moorestown, N. J., assignor toRadio Corporation oi America, a corporation of Delaware ApplicationJanuary 31, 1950, Serial No. 141,465

8 Claims.

My present invention relates to sound reproducing diaphragms, and moreparticularly to an improved base suspension for conoidal, dynamicloudspeaker diaphragms having an elliptical base periphery.

The structure of conventional elliptical conetype diaphragms for dynamictype loudspeakers, generally, consists of a main body portion ofconoidal shape, the base periphery of which is elliptical, with the apexend terminating in a collar to which a cylindrical voice coil form isattached. The base end of the body portion terminates in a radiallyextending flange or rim provided with one or more radial corrugations,with the outer periphery thereof adapted for clamping or otherwise beingsecured to a support, such as a conventional dishpan support. The mainbody portion functions as the sound reproducing portion, while theflange, or rim, functions primarily as a flexible support for the bodyportion permitting it to move freely in directions parallel to itscentral axis. As far as the production of sound is concerned, theflange, or rim, has little, if any, function. However, unless it isproperly constructed, its stiffness and inertia will adversely affectthe natural period of vibration of the main body portion with aconsequent loss in efficiency and acoustical qualities of theloudspeaker of which it forms a part.

Although conventional, prior art, elliptical cone-type diaphragms havebeen found to operate with satisfactor results, they are also found topossess certain disadvantages which are attributable to certainstructural features of the flexible base suspension for the main bodyportion of the diaphragm. For example, in the conventional diaphragm,the flange, or rim, is of uniform width around the entire periphery ofthe base of the main body portion. Since the corrugations are also ofuniform width and follow the elliptical pattern of the base peripherythey offer greater stiffness at the portions thereof disposed in thedirection of the major axis or" the elliptical base periphery than theportions thereof disposed in the direction of the minor axis. This isdue to the fact that the radius of curvature of the corrugations isshorter in the vicinity of the major axis than in the vicinity of theminor axis. Inasmuch as the flange, or

rim, is stiffer along the major axis than along the minor axis, itoffers more resistance to axial motion of the main body portion of thedia phragm along the major axis. This difference in resistance resultsin distortion of the cone and disturbance of uniform oscillationsthereof. Furthermore, since the curvature of the corrugations along themajor axis is greater than the curvature along the minor axis, thecorrugations are subjected to greater stress and strain along theportions thereof disposed along the major axis. During normal operationof the diaphragm, the flange, or rim, is, therefore, more readilysubject to rupture in the region adjacent the major axis.

The primary object of my present invention, therefore, is to provide animproved flexible base suspension which will overcome the above as wellas other disadvantages of prior art base suspensions for elliptical,cone-shaped, diaphragins.

Another object of my present inve tion is to provide a flexible supportfor the elliptical base periphery of conoidal diaphragms which will haveapproximately uniform flexibility or stillness at all points about theelliptical base pe riphery.

Still another object of my present inven is to provide a resilientsupport for the pe edge of an elliptical, conical-shaped diap whereinthe resilient support is less subject to destruction arising out of thecontinued vihrations of the diaphragm.

A still further object of my present invention is to provide anelliptical colloidal-type diaphragm for use in sound reproducinginstruments which will have a base support having substantially uniformstiffness at all points about the diaphragm base periphery.

In accordance with my present invention, I provide a conical-shapedsound reproducing diaphragm having an elliptical base periphery with aflexible base support comprising a corrugated rim the structure of whichhas substantially uni form stiffness around the entire periphery of thediaphragm base. In accordance with one modification, the rim andcorrugati 11s are made of gradually increasing widths in directionsextei ing around the base periphery from the region adjacent the minoraxis to the region adjacent the major axis of the base periphery.According to another modification, the Width of the made increasinglylarger in the same in the aforementioned modification but thecorrugations are of uniform width and increase in number with theincrease in width of the The novel features characteristic of myinvention, as well as additional objects and advantages thereof, will bebetter understood from the following detailed description when inconnection with the accompanying drawing in which:

Figure 1 is a front view of a conical sound reproducing diaphragm havingan elliptical base periphery in accordance with one modification of mypresent invention,

Figure 2 is a sectional view of the diaphragm shown in Figure 1, takenalong the line 2--2 of Figure 1,

Figure 3 is a sectional view similar to Figure 2, taken along the line33 of Figure 1,

Figure 4 is a view similar to but somewhat smaller than that shown inFigure 1 of a second embodiment of a sound reproducing diaphragm inaccordance with my invention,

Figure 5 is an enlarged, sectional view of a portion of the diaphragmand base support shown in Figure 4, taken on the line 5-5 of Figure i,

Fig. 6 is a view similar to Figure 5, taken on the line 58 of Figure 4,and

Figure 7 is a view similar to Figure 5, taken on the line 1-1 of Figure4.

Referring more particularly to the drawing, wherein similar referencecharacters desi nate corresponding parts throughout, there is shown inFigures 1 through 3 an elliptical, conoidal, sound reproducing diaphragml which comprises a main bodyv or sound reproducing portion 3, and aperipheral support therefor comprising a rim or flange 5 which extendsfrom the elliptical base periphery i of the main body portion 5. Theapex end of the main body portion 3 terminates in a collar or circularflange 9 for attachment, in suitable manner, to the voice coil of adynamic loudspeaker.

The rim or flange 5 is radially corrugated, that is, it is provided withone or more circumferential corrugations or undulations ii, the valleysand peaks of which ar arranged successively outwardly from theelliptical base periphery I of the diaphragm body portion 3.

In the process of reproducing sound, the loudspeaker voice coil drivesthe diaphragm main body portion 3 in axial directions, that is, indirections parallel to the central axis of the dia-, phragm, with thesound output and natural period of vibration of the diaphragm dependingupon the flexibility of the supporting rim or flange 5. Due to theelliptical contour of the base periphery i, the rim 5 has greaterresistance to movement of the main body portion 3 near its shorterradius of curvature which is disposed in the region of the long or majoraxis 13 of the elliptical base periphery 5 and less resistance tomovement of the body. portion near its longer radius of curvaturedisposed in the region of the short or minor axis l5. Because of theuneven d stribution of stiffness throughout the length of the rim 5, thenatural period of vibration of the body portion 3 is adversely affectedwith a consequent loss in sound reproducing quality and efficiency. Inaddition, the portions of the rim 5 in the region of the major axis [3are more readily subject to fracture because of this uneven distributionof stiflness.

In order to overcome these difiiculties, I; provide a rim or flange 5 ofgradually increasing width in directions extending about the baseperiphery from the region adjacent the minor axis [5 to the regionadjacent the major axis l3, as best illustrated in Figures 2 and 3 ofthe drawing. Accordingly, it will be recognized by those persons skilledin the art, that because of the increase in width of the rim 5, it willbe more flexible at the wider portions thereof and con-. sequently have.less stiffness at those portions. With proper design, the rim 5 may bemade to have uniform stiffness around the entire length of the baseperiphery 7 of the elliptical diaphragm i. This may be accomplished byincreasing the rim width approximately in direct proportion to thedistance the elliptical base periphery 1 is disposed from the diaphragmcentral axis IT, or, approximately in inverse pro-,

portion to the radius of curvature of the base periphery 1.

The rim corrugations ll either may be ofequal number around the entirelength of the rim 5, as shown particularly in the modificationillustrated in Figures 1 through 3, or they may vary in number, as shownparticularly in the modiflcation illustrated in Figures 4 through 7. Ifthey are of equal number, the widths of the corrugation H are made toincrease approximately in direct proportion to the width of the rim 5-.However, if the corrugations vary in number, their widths are uniformthroughout their length and they increase in number with the increase inwidth of the rim 5. For example, as shown in the modificationillustrated in Figures 4 through 7, there are two radial corrugations IIin the region of the minor axis l5, and three radial corrugations l l inthe region of the major axis !3.

Thus, it will be recognized that by varying the width of the flange orrim which supports the sound reproducing elliptical diaphragm at thebase periphery, and additionally varying either the width of thecorrugations or their number, in the manner described above, thestiffness of the rim may be controlled in such a manner that it willhave approximately uniform stiffness at all points around the diaphragmbas periphery. Furthermore, the stresses in the material will besubstantially equalized with the result that the material will be lesssubject to fracture and the efiiciency of the diaphragm greatlyenhanced.

It will be recognized by those persons skilled in the art, that I haveprovided an improved flexible support for the base periphery ofelliptical, conoidal sound reproducing diaphragms. While I havedescribed and illustrated but two embodiments of my present invention,it will also be recognized that various changes and modifications arepossible within the spirit of my invention. Therefore, I desire that theparticular form of my invention described herein shall be considered asillustrative and not as limiting.

What is claimed is:

1. A cone-type sound reproducing diaphragm having an elliptical baseperiphery and a flexible collar having a radially corrugated portionextending from said base periphery, the width of the radially corrugatedportion of said collar increasing in dimension from the portion thereofin the region adjacent the minor axis of said base periphery to theportion of said collar in the region adjacent the major axis of saidbase periphery.

2. A sound reproducing diaphragm according to claim 1 wherein the widthof the radially cor-. rugated portion of said collar variesapproximately in direct proportion to the distance said base peripheryis disposed from the diaphragm central axis.

3. A cone-type sound reproducing diaphragm having an elliptical baseperiphery and a flexible collar having a radially corrugated portionextending from said base periphery, the width of the radially corrugatedportion of said collar increasing in dimension from the portion thereofin the region adjacent the minor axis of said base periphery to theportion of said collar in the region adjacent the major axis of saidbase periphery, the width of the radially corrugated portion of saidcollar varying approximately in direct proportion to the distance saidbase periphery is disposed from the diaphragm central axis, and theWidth of each corrugation varying directly with the width of saidcollar.

4. A cone-type sound reproducing diaphragm, having anelliptical baseperiphery, andaflexie. is. adial q ms ted fla ge. exten in from,

said base periphery, the width of said flange from said diaphragm baseperiphery to the outer periphery of said flange varying approximately ininverse proportion to the radius of curvature of said base periphery,and the width of each corrugation varying directly with the width ofsaid flange.

5. In a conoidal type dynamic loudspeaker diaphragm having a baseperiphery of elliptical shape, a flexible rim for said diaphragmextending from said base periphery for supporting said diaphragm forrelatively free axial movement, said rim having a plurality ofcorrugations the valleys and peaks of which are arranged successivelyoutwardly from said base periphery and of equal number throughout thelength of said rim, the width of the portion of said rim having saidcorrugations increasing in dimension between the portions disposedrespectively in the region thereof opposite to the minor and major axesof said base periphery, the Width of each of said corrugations varyingdirectly with the width of said rim, said width dimension varyingapproximately as a function of the distance said base periphery isdisposed from the diaphragm central axis whereby said rim and saidcorrugations will offer approximately the same resistance to axialmovements of said diaphragm at all points about said base periphery.

6. In a conoidal type dynamic loudspeaker diaphragm having a baseperiphery of elliptical shape, a flexible rim for said diaphragmextending from said base periphery for supporting said diaphragm forrelatively free axial movement, said rim having a plurality ofcorrugations the valleys and peaks of which are arranged successivelyoutwardly from said base periphery, said corrugations being of uniformwidth, the width of the portion of said rim having said corrugationsincreasing in dimension between the portions disposed respectively inthe region thereof opposite to the minor and major axes of said baseperiphery, said corrugations increasing in number with the increase inwidth of said rim,

said width dimension varying approximately as a function of the distancesaid base periphery is disposed from the diaphragm central axis wherebysaid rim and said corrugations will offer approximately the sameresistance to axial movements of said diaphragm at all points about saidbase periphery.

7. An acoustic diaphragm of the direct acting type comprising a bodyportion of conoidal shape having the base periphery thereof defining anellipse, and a peripheral flange for supporting said body portionextending from said base periphery, said flange being provided with atleast one circumferential corrugation thereby to flexibly support saidbody portion for freedom of movement in directions axially thereof, saidcorrugation and said flange increasing in width from the portionsthereof disposed in the plane including the central axis of said bodyportion and the minor axis of said base periphery to the portionsthereof disposed in the plane including the central axis of said bodyportion and the major axis of said base periphery.

8. In a conoidal type dynamic loudspeaker diaphragm having a baseperiphery of elliptical shape, a flexible rim for said diaphragmextending from said base periphery for supporting said diaphragm forrelatively free axial movement, said rim having a plurality ofcorrugations the valleys and peaks of which are arranged successivelyoutwardly from said base periphery, the width of the portion of said rimhaving said corrugations increasing in dimension between the portionsdisposed respectively in the region thereof opposite to the minor andmajor axes of said base periphery, said width dimension varyingapproximately as a function of the distance said base periphery isdisposed from the diaphragm central axis whereby said rim and saidcorrugations will offer approximately the same resistance to axialmovements of said diaphragm at all points about said base periphery.

ROBERT E. HURLEY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,722,805 Lane July 30, 1929 1,825,833 Tennessee at al Oct. 6,1931 1,913,451 Lane June 13, 1933 1,930,328 Tichenor et al Oct. 10, 19332,358,823 OConnor Sept. 26, 1944

